Method of printing on non-absorbent material



Jan. 5, 1965 L. J. BRQWNING METHOD OF PRINTING 0N NON-ABSORBENT MATERIAL.-

Filed Aug. 24, 1962 [ESL IE JOHN BROWN/N6 labia. M m

ATTORNEYS United States This invention relates in general to printing means and a method of printing, and in particular to a new and useful off-set printing mechanism for printing on a stable material such as a plastic, including means for feeding the stable material to be printed, so that double inking of the blanket takes place for every impression transferred by the blanket to the stable material, and to a method of printing such stable material.

The present invention relates to off-set lithographic printing, wherein a plate carrying an image is used to make an ink impression on an off-set blanket, from which the impression is then transferred to the material to be printed. The plate and the blanket are usually each carried on a cylinder and the material to be printed is carried on a third impression cylinder arranged for moving the material to be printed in contact with the blanket. The pressures between the surfaces of the impression roller and the blanket have to be adjusted to obtain a correct transfer of ink. Printing machines of this character generally include an automatic means for advancing the material to be printed between the impression roller and the blanket once for every revolution of the blanket cylinder.

A difficulty in the operation of such machinery is to obtain a sufiiciently heavy image transfer from the blanket, because by its very nature the off-set printing process severely limits the quantity of ink that can be transferred. This is particularly acute in connection with printing on sheet material hereinafter called a stable material, such as plastic, polystyrene, cellulose acetate, polyvinyl-chloride and the like, which have non-absorbent and shiny surfaces. Prior to the present invention such printing has been done by the so-called silk screen method in which a silk screen is employed as kind of a stencil and the ink is pressed through the screen. A disadvantage in such a process is that the equipment is costly and the operation is slow and consequently only suitable for use in rather special cases and then only for short runs. A further difliculty of the silk screen process is that the coating so applied is so thick that even if transparent colors are used, each coating completely hides any underneath coating, making it diflicuit to blend colors by superimposing layers of different colors. A further ditficulty is that by the silk screen process it is not possible to produce half tone printing finer than sixty lines. Attempts to build up a heavy image in offset lithographic printing by the use of double printing according to which the material is passed twice through the machine is not satisfactory, due to the difiiculty of obtaining an accurate registration of the separately applied images.

A further difiiculty of the treatment of non-absorbent material such as plastic is that the ink is relatively slow in drying when compared with the speed of operation of the machine, and the material is highly finished, so that when the printed material is stacked, intimate contact is made between adjacent sheets and some degree of set-off is unavoidable. This set-off action causes a reduction in the density of the image, and usually causes smudging. In addition, the blurred and imperfect image set off on the back of the material is unsightly and can render the product unsuitable for certain uses.

In accordance with the present invention there is proatent ice vided an apparatus and method for handling stable material such as a plastic, which includes means for feeding such material into contact with an inking blanket, only after the blanket has been doubly inked. In the preferred method, the stable material is advantageously interleaved with a much thinner material and the usual printing machines are operated in an ordinary manner. The machine is operated in the usual manner, and since the plastic material is interleaved with the thin material, a thin sheet of material is fed between the impression roller and the blanket roller first before each sheet of stable material. The thin material is made sufliciently thin and the clearance between the transport roller and the blanket roller adjusted, so that the thin material does not pick up any impression from the blanket. Thus, with an ordinary printing machine operating in the usual manner, it is possible to permit the blanket roller to receive a double inking before the impression thereon is transferred to the stable material which is to be printed.

While a preferred arrangement is to utilize the usual printing equipment in ordinary maner, it is also possible to achieve printing of the stable material without first interleaving the material with thin sheets, as described above. For such an arrangement feeding means are provided to advance the stable material to be printed between the impression roller and the blanket roller only once for every two times the blanket roller is rotated in contact with the ink transfer roller. As can be seen, the advancement of the stable material to be printed in this manner may be done by adjusting the feeding mechanism by the machine or by interleaving, as shown herein.

Accordingly, it is an object of this invention to provide an improved off-set printing apparatus and method of printing.

A further object of the invention is to provide an improved method of lithographic off-set printing on sheets of stable, non-absorbent material, comprising first interleaving the sheets of material with sheets of a thinner material and thereafter advancing the combined stack through a machine adjusted so that the thinner material receives no impression from the blanket cylinder and the stable material is effectively printed only after the blanket roller has been rotated past the ink transfer roller and the impression cylinder twice.

A further object of the invention is to provide a device for printing sheets of stable material, including a printing roller and a transport roller rotatably mounted to define a clearance between the peripheries thereof, an impression roller arranged to contact said blanket roller during each cycle of operation for transferring an ink impression thereto, and means for feeding interleaved sheets of stable and thin material between the clearance of said blanket roller and said transport roller, the thin material being of a dimension so that it passes between said rollers without receiving an impression from said blanket roller, the blanket on said blanket roller being moved into contact with the impression roller twice before each stable material sheet is printed.

A further object of the invention to to provide a method of printing stable material in a machine having a blanket roller adjusted to the thickness of the stable material, which comprises interleaving the stable material with a sheet of material thin enough to be fed past the blanket roller without receiving an impression therefrom, thereafter directing the interleaved stack into an ordinary printing machine for operation thereon by the blanket roller to print on the stable material, the thin material passing through without obtaining any printing thereon.

A further object of the invention is to provide a printing apparatus and method which is simple in design and concept, effective in construction and operation, and economical to manufacture and carry out.

are gose The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a somewhat schematic side elevation of a printing machine for carrying out the preferred method of printing of a stable material in accordance with the invention; and

FIG. 2 is a view similar to FIG. 1 but indicating an interleaved thin sheet being fed between the blanket cylinder and transport cylinder without receiving an impression from the blanket.

Referring to the drawing in particular, the invention embodied therein includes a printing machine having an ink duct roller 2 which is fed from an ink duct or reservoir 4 formed between it and a doctor blade or plate 6. Arranged adjacent the ink duct roller 2 at a slightly lower elevation and to one side thereof is a composition ink roller 8, and an ink duct vibrator roller is movably mounted between the ink roller 8 and the ink duct roller 2. The ink duct vibrator roller 10 is mounted so that it alternatey makes contact with both the composition ink roller 8 and the ink duct roller 2 to pick up ink from ink duct roller 2 and transfer it evenly to the surface of the composition roller 8 as it rotates. The ink duct vibrator roller 10 is advantageously not driven but is rotated by the motion imparted thereto by repeated contact with the surfaces of the continuously rotating ink duct roller 2 and composition roller 8.

Directly vertically beneath the composition roller 8 is arranged a copper transfer roller 12 which rotates in contact with the composition roller 8 and transfers ink therefrom to an ink roller 14 directly therebelow which, in turn, rotates in contact with a steel inking drum 16. In this manner the steel inking drum 16 receives a constant and evenly distributed supply of ink from the ink duct 4.

The steel inking drum 16 is reciprocated axially in a known manner, and located a short distance therebeneath is mounted a plate cylinder 18 which is adapted to carry the plate bearing image to be printed. The transfer of ink to the plate is accomplished through the plate cylinder 16 in a known manner through the chains of'rollers, including ink transfer rollers 2t) and 22 on each side of the plate cylinder 16 which are in rolling contact with two copper ink rollers 24 and 26, respectively, and two ink plate rollers 28 and 30, respectively. The two trains of rollers 24, 26 and 28 and 30 are spaced apart and arranged diverging so as to transfer the ink to the plate cylinder 18 at points which subtend at an angle of about 90.

Since in lithographic printing it is essential to damp the plate 18, there is provided on the right-hand portion of the plate cylinder 2. water duct roller 32 located in and partly emerged in water contained in a water reservoir or duct 34. In contact with the plate cylinder 13 are two plate damper rollers 36 and 38, and between and in contact therewith is a copper oscillating roller 4%. A damping vibrator roller 41 is located between the copper oscillating roller 40 and the brass water duct roller 32 and it is'movably mounted, so that it picks up water from the water duct roller 32 and transfers it to the copper oscillating roller 40. This imparts a film of water to the two plate damper rollers 36 and 38 which, in turn, moisten the printing plate cylinder 13.

A blanket cylinder 42 containing a blanket (not indicated) is situated in rolling contact with the plate roller 18, so that the ink impression thereof is rolled off on the blanket during each revolution of the rollers 42 and 18. An impression cylinder or transport cylinder 44 is arranged beneath the blanket cylinder 42' but out of contact therewith, the blanket cylinder 42 and the impression cylinder 44 being relatively adjustable so that the clearance therebetween can be set according to the thickness of the material to be printed. Hence, suitable adjustment means may be used, such as an eccentric bearing mounting, for example, which is well known.

In FIG. I a highly polished sheet 46 of polystyrene or other stable material having a thickness of 0.02 inch, is fed between the blanket cylinder 42 and the impression cylinder 44. The machine employed for the carrying out of the method of the invention is advantageously adjustable for the printing of material in a thickness range from one one hundredth to four one hundredths of an inch, that is between 0.01 and 0.04 inch.

In FIG. 2 of the drawings there is indicated passing through the nip formed between the impression cylinder 44 and the blanket roller 42 a sheet of thin material as which has advantageously been interleaved with the stable material as by machinery provided at the right of the printing machine indicated in FIGS. 1 and 2. In the example illustrated, the thin sheet material 58 has the thickness of 0.005 inch, that is, five one thousandths of an inch. The thickness of the interleaved sheet may be varied according to availability and suitability. The drawing obviously exaggerates the dimension of the gap between the blanket cylinder 42 and the impression cylinder 44.

In accordance with the invention, it has been found that the interleaving sheets as may advantageously comprise an unglazed, slightly rough surface material which is reasonably receptive to ink. A paper known in the trade as M.G. poster paper has been found suitable. In the arrangement indicated, a thin sheet is fed between the cylinders 42 and 44 once and then a stable material sheet is fed thereafter. The sheets are advantageously collected by suitable collecting means (not shown) in a vertical stack 50 in which the stable plastic sheets 46 remain alternately arranged or interleaved with the thin sheets 48. Suitable means are provided to stack the sheets vertically, and the interleaved stack may, of course, be used for successive printing operations, such as for a multicolor printing, for example. When color printing is done, a number of impressions has to be made on each sheet. This is done by transferring the stack of alternately arranged plastic and thin paper sheets from the delivery side ofthe machine to the feed side of the same machine or another machine in which the next impression is to be made, and the process is repeated. The printing machines advantageously include means for aligning the sheets for correct orientation and feeding into association with the blanket on the blanket cylinder 42. Since the sheets are already interleaved after each operation, it is a simple matter to feed them through for a new printing operation, when desired.

The invention may be embodied otherwise, such as in a machine which has a feeding mechanism for feeding the stable sheets which are not interleaved with thin sheets between the impression and blanket cylinders only after the blanket on the blanket cylinder has been rotated in contact with the plate cylinder 18 twice. Thus, the blanket arranged on the blanket cylinder 42 receives two separate ink impressions for each impression imparted onto the stable material sheet.

An advantage of the printing method in which the stable sheets are interleaved with thin sheets is that the thin sheets are fed generally over the surface of the plastic sheets after they are printed, and the weight of the stack is not pressed down by the weight of the next plastic sheet until the next cycle of operation of the printing machine, at which time the previously inked stable plastic sheet will have dried sufiiciently to avoid any smudging or rubbing off of the printed material.

ln accordance with the preferred method, the process may be initiated by interleaving the plastic and paper sheets manually or by any suitable mechanical feeding arrangement for interleaving sheets together. In some instances a double feed arrangement may be incorporated in the feed to the impression and blanket cylinders, so that first a paper sheet and then a plastic sheet is fed thereto. two or more thin sheets with the plastic sheet for the purpose of providing an increased inking time and a longer drying time between each delivery of printed material.

With the method and apparatus described it has been found that an impression can be transferred from the blanket to a sheet of polystyrene of a density equivalent to that only heretofore obtainable by double printing and of course the problem of registration of the image on the second printing is eliminated. Half tone work equal to letter press printing is obtained. The interlaid sheets of poster paper receive no noticeable impression, and the roughness of the back allows the material to be stacked without set-off or smudging, provided that the size of the stack is limited to a predetermined size easily determinable. If a sheet of poster paper was deliberately omitted, set-off and smudging has been found to occur immediately.

Another advantage in color printing by the method of the invention is that the interleaved sheets remain in the stack after each printing, so that the interleaving only has to be effected once irrespective of the number of printing steps.

Recovery of the interleaved material can be effected, but in practice it has been found that to leave the sheets of poster paper in the stack reduces the risk of damage to the impression in transit.

Since the above process has enabled lithoprinting to be used for printing on plastics, the thinner layers inherent in lithoprinting, as compared with the silk screen process, enable superimposed colors to be used for obtaining color blending, thus reducing the number of workings required for any desired color effect.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. A method of printing a stable material having a substantially non-absorbent, shiny surface with a printing press having a printing roller and an impression cylinder,

In some instances it is desirable to incorporate comprising interleaving a relatively thick sheet of such stable material with a thin sheet of a paper material and feeding the interleaved sheets through the printing press which is arranged with the printing roller spaced from the impression cylinder by an amount at least greater than the thickness of thethin sheet but sufficient to imprint the stable sheet.

2. A method according to claim 1, including collecting the sheets in a vertical stack, wherein the interleaved paper sheets form a protective covering for the imprinted stable sheets.

3. A method according to claim 2, including passing the collected stack through another printing operation identical to the first for effecting a different printing impression thereon.

4. A method of offset printing employing a blanket cylinder arranged adjacent an impression cylinder, a plate roller arranged to wipe the blanket roller once during every operation of the blanket cylinder, and thin interleaving sheets of a size to pass between the blanket cylinder and impression cylinder wi-thout receiving an impression, comprising interleaving a plurality of the thin interleaving sheets with sheets to be printed and directing the interleaved sheets between the impression cylinder and the plate cylinder whereby the thin interleaving sheets are passed between the rollers without receiving an impression and the sheets to .be printed receive an impression only after a plurality of revolutions of the blanket cylinder in contact with the plate cylinder.

References Cited by the Examiner UNITED STATES PATENTS 237,558 2/81 Lee 101-151 1,143,708 6/15 Heinrich 271-30 1,528,660 3/25 De Sperati 101-217 1,897,148 2/33 Rowell 101-217 1,942,490 1/34 Quigley 271-56 1,974,544 9/34 Rowell 271-56 2,270,273 1/42 Davidson 101-217 X 2,675,232 4/54 Cardenas et a1. 27'1-56 2,898,853 8/59 Wadlow 101-217 2,948,215 8/60 Tyma et a1. 101-247 X 3,076,407 2/ 63 Zimmerman 101-247 X EUGENE R. CAPOZIO, Primary Examiner.

ROBERT A. LEIGHEY, ROGERT E. PULFREY,

' Examiners 

4. A METHOD OF OFFSET PRINTING EMPLOYING A BLANKET CYLINDER ARRANGED ADJACENT AN IMPRESSION CYLINDER, A PLATE ROLLER ARRANGED TO WIPE THE BLANKET ROLLER ONCE DURING EVERY OPERATION OF THE BLANKET CYLINDER, AND THIN INTERLEAVING SHEETS OF A SIZE TO PASS BETWEEN THE BLANKET CYLINDER AND IMPRESSION CYLINDER WITHOUT RECEIVING AN IMPRESSION, COMPRISING INTERLEAVING A PLUALITY OF THE THIN INTERLEAVING SHEETS WITH SHEETS TO BE PRINTED AND DIRECTING THE INTERLEAVED SHEETS BETWEEN THE IMPRESSION CYLINDER AND THE PLATE CYLINDER WHEREBY THE THIN INTERLEAVING SHEETS ARE PASSED BETWEEN THE ROLLERS WITHOUT RECEIVING AN IMPRESSION AND THE SHEETS TO BR PRINTED RECEIVE AN IMPRESSION ONLY AFTER A PLURALITY OF REVOLUTIONS OF THE BLANKET CYLINDER IN CONTACT WITH THE PLATE CYLINDER. 